The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Androgens are required for the masculinization of male genitalia in utero, the development of secondary sex characteristics in boys, and the maintenance of male sexual function in adult life. After entering the target cell, androgens bind to androgen receptor (AR)--a ligand-dependent transcription factor. After binding of the hormone, AR enters the nucleus and binds to the regulatory region of the target gene as a homodimer. AR belongs to the nuclear receptor superfamily comprising receptors for various forms of vitamin D.sub.3, thyroid hormones, retinoids, and steroid hormones (1). These receptors have conserved DNA--and ligand-binding domains (DBD and LBD, respectively), and variable hinge and N-terminal regions (1). In the case of AR, the N-terminal region encompasses the primary transcriptional activation domain. Upon androgen binding, LBD and the N-terminal region of AR have been shown to interact, which is suggested to facilitate AR dimerization (2,3), modulate transcriptional activity (4), and stabilize the receptor at low ligand concentrations (5).
AR-interacting protein 3 (ARIP3), a 572-amino acid nuclear protein expressed primarily in the testis, represents a potential coregulator of AR-dependent transcription (6). Although the exact physiologic role of ARIP3 is not yet known, we have observed that it can considerably facilitate the androgen-dependent interaction between the AR LBD and N-terminal region (6). Herein, we report the development of a bioassay that is based on ARIP3-facilitated interaction between the LBD and N-terminal region of AR. This assay appeared useful for quantitation of circulating androgen bioactivity in pediatric patients. We expect that the assay will have wide ramifications in clinical endocrinology.